1. Field of the Invention
The present invention relates to apparatus and methods for forming signatures from a collated stack of documents, and more particularly to copying apparatus and methods of using copying apparatus for outputting signatures from a collated stack of documents which are placed directly in a document handler of the copying apparatus without any manual or automatic preordering of the documents, and which are fed from the document handler directly to the imaging platen of the copier for imaging.
2. Description of Related Art
A signature is a sheet containing plural (usually 4) printed pages (page images), usually two on each side, with a page arrangement such that when such signature sheets are center-folded and nested one inside of the other with other signature sheets in a set they become one collated pamphlet, booklet, or book; or a quire forming one section of a larger book. The booklet copies may be formed from center-folded sheets of paper each carrying four copy images of the original documents made in a known signature page sequence. A particular, known, non-directly-sequential placement of images on each signature sheet is essential to providing a completed signature set or booklet with a proper direct sequential page order.
It is not surprising that signature copying, even though it is a desirable function or feature, is not commonly practiced on copiers except by experienced operators, and is very error prone. With manual document handling, one slip in any of the complicated processes of document page reordering and variable orientation and sequencing of document placement and spacing will result in unusable book copies, and the job must be redone.
U.S. Pat. No. 4,708,469 to Bober et al. discloses an interactive system for signature production which responds to operator input data defining the total number of pages in a document to be signature printed by displaying the pagination of the signatures, illustrating for the operator the proper signature orientation. The system also calculates a check value for use in determining whether the correct pages have been copied onto each signature. This system requires manual placement of the original documents on the copier platen, and thus introduces the possibility of errors and also requires a great deal of time to precisely align each pair of documents on the platen.
U.S. Pat. No. 4,727,402 to Smith discloses a system for automatic signature set production in which a collated stack of documents is first placed onto an automatic document reordering and presenting system which reorders the documents into the appropriate signature order by selectively feeding the documents to one of two stacks located in a dual feeding recirculating document handler (RDH). Once the documents have been preordered into the appropriate signature order, and placed into the two stacks in the RDH, the documents are fed two at a time (i.e., a sheet is simultaneously fed from each stack in the dual feeding RDH) to the copier imaging platen for "two-up" copying onto one side of a signature copy sheet. The automatic document reordering and presenting system can include a bottom-feeding conventional RDH which requires that the collated stack of documents placed therein be recirculated therethrough in order to place the documents in the two stacks formed in the dual feeding RDH in the appropriate signature order. As an alternative, a document feeder which alternately feeds from the top and bottom of the collated stack of documents can be used in the automatic document reordering and presenting system (see FIG. 12 and column 19, lines 26-44). In either case, a separate system is required to reorder and present the documents to the dual feeding RDH which feeds to the copier platen. Additionally, because the system of U.S. Pat. No. 4,727,402 is a high speed copier in which copy sheets are fed therethrough long-edge-first, the document sheets whose images are to be copied onto one side of a signature copy sheet must be rotated 180.degree. with respect to the document sheets whose images are to be copied onto the opposite side of the same signature sheet (see column 18, lines 36-44). Accordingly, a sheet rotator is also placed between the input tray of the automatic document reordering and presenting system and the dual feeding RDH which feeds the signature ordered documents to the copier platen.
U.S. Pat. No. 4,925,176 to Thomas Acquaviva discloses a signature job copying system in which signature ordered document sheets are fed long-edge-first from a RDH sequentially so as to be placed two-at-a-time on the copier imaging platen for copying onto a signature copy sheet which is fed short-edge-first through the copier. The system of U.S. Pat. No. 4,925,176 also requires a special reordering system (an "automatic job loading system") for reordering the documents into the appropriate order for signature copying, and for feeding the reordered documents to the copier RDH. Moreover, the operator can not place a collated stack of documents into the automatic job loading system, but must first properly orient (i.e., invert) about the lower half of the documents in the stack prior to insertion into the automatic job loading system. This inversion introduces the possibility of errors, and the determination of which documents are to be inverted is not always straight forward.
U.S. Pat. No. 4,592,651 to T. Oikawa, et al. (Ricoh) shows a copier with a duplex recirculating document handler and a center-folding book-binding device for the signature copies. Of particular interest, cols. 14-15 describe some signature copying formulas and cols. 15-16 describe document copying sequences using immediate duplexing. However, this system requires 4 copying passes for each copy sheet being signatured, and requires immediate duplex document inversion.
All references cited in this specification, and their references, are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background.